What was the key difference between Marconi's 1895 telegraphy and the 1915 milestone?

1895 transmitted data (telegraph signals), while 1915 transmitted voice.

Marconi's original system sent coded electrical pulses, essentially dots and dashes like Morse code, through the air. This was wireless telegraphy.

In 1915, the first wireless voice (speech) communication was achieved between New York and San Francisco. This was wireless telephony, a much harder problem because voice requires transmitting a continuous, complex analog waveform rather than simple on/off pulses.

Why it matters: This shift from data to voice laid the groundwork for all mobile phone technology. Every generation from 1G through 4G was fundamentally about carrying voice. It wasn't until the smartphone era that data overtook voice as the primary use case.